I thought I'd start a discussion of the presocratic philosphers by recommending a very good book about them. The book, , is one of the best sources about them. Take for example Heraclitus. It is very hard to find a good source about his writing as translation is quite complicated. There aren't many other sources for the greek he uses, so much is made up by the translator, and as with all deep philosophy, small mistranslations can easily turn every text to banl and stupid. Both I think their translation is the best I've seen (unless you start investigating word for word, as Heidegger does in his seminar on Heraclitus, , which is both limited in scope, and comes with a philosophical agenda which many would disagree with). 

They don;t merely provide a translation but arrange in a comprehensive way, which is both very understandable and convincing. Obviously, the scope of the book demands briefness and lack of precision, but it gives you a very quick look at them.

The book discusses 15 philosophers/philosophies and gives a very good introduction to their thoughts.
For a personal, philosophical, view on the presocratic there is Nietzsche's book:  .

The presocratics are extremely different from the post socratic philosophers, socrates being in between. The post socratic are the philosophers of the Academia, aspiring to a philosophy which rejects the body for an almighty mind, and mostly, a rejection of our world for a philosophical I, a transcendental/ontological I, and represent what most people today associate with philosophy.On the other hand, the presocratic, are interested in the experiance of living in the real world (yes, even Zeno and Parmenides).
The presocratics are thus both very different from today's philosophers, but still, clearly philosophers and not artists. Thus they also provide a pathway for a thought of the difference of philosophy and art.

To conclude, highly recommended. Their philosophy seems to me to speak more pertanitely to our current situation than much of the post socratic.